1. Field of the Invention
The present invention relates to a digital decimation filter used for a device such as an over sampling A/D converter.
2. Description of the Related Art
In general, a digital decimation filter is three-dimensional moving average filter having a transfer function expressed by the following equation. A decimation ratio n which indicates a ratio of an input sampling frequency to an output sampling frequency i a fixed integer; EQU H (Z)={(1-Z.sup.-n)/(1-Z.sup.-1)}3 (1)
where Z is a complex number.
In such a digital decimation filter, the decimation ratio n is utilized to simultaneously control input and output sampling clocks, and the decimation ratio n is a fixed integer.
The above conventional digital decimation filter has a problem in that it is not possible to arbitrarily change the decimation ratio because the value of n is fixed.